Conventional microelectronic devices are manufactured for specific performance characteristics required for use in a wide range of electronic equipment. A microelectronic bare die, for example, includes an integrated circuit and a plurality of bond-pads electrically coupled to the integrated circuit. The bond-pads can be arranged in an array, and a plurality of solder balls can be attached to corresponding bond-pads to construct a “ball-grid array.” Conventional bare dies with ball-grid arrays generally have solder balls arranged, for example, in 6×9, 6×10, 6×12, 6×15, 6×16, 8×12, 8×14, or 8×16 patterns, but other patterns are also used.
Bare dies are generally tested in a post-production batch process to determine which dies are defective. To protect the dies during testing and other post-production processes, a protective coating is formed over the surface and/or edges of the dies. One drawback of forming the protective coating on conventional dies is that the coating material can interfere with the connection between the solder balls and the contacts of a testing device and, accordingly, result in false negative tests and the loss of good dies. Thus, there is a need to improve the process of forming the protective coating on bare dies.
In other applications, bare dies and various other packaged dies can include an underfill layer across the surface of the dies to (a) protect the dies from moisture, chemicals, and other contaminants, and (b) enhance the integrity of the joint between the individual dies and the corresponding substrates to which the dies are subsequently attached. The underfill layer can be formed on the die before the die is attached to the substrate, and the layer typically has a thickness of between approximately 70 and 90 percent of the height of the solder balls on the die.
One drawback of conventional processes for depositing underfill across the die is that the underfill material also wicks up and may cover the top of the solder balls. Consequently, the underfill typically does not include dielectric filler particles because if the particles were to become trapped on the tops of the solder balls, the particles would impair the subsequent electrical connection between the die and the substrate. It is, however, desirable to use underfill with filler particles because the particles increase the rigidity of the underfill to provide a more robust package. Accordingly, there is also a need to improve the process of depositing underfill material on dies.